1. Field of the Invention
The invention relates to an apparatus for pile-driving or drilling, particularly a foundation machine.
2. Description of the Related Art
Leader-guided vibration pile drivers as well as drilling devices and foundation machines in general are regularly operated hydraulically. In this connection, an open hydraulic circuit is used, because in this way, in contrast to a closed circuit, the operation of different work devices, such as, for example, vibrators, drilling drives, presses, etc., as well as a switch between different consumers such as a work device or a drive of a crawler track drive is made possible. The open hydraulic circuit has a control block or valve block, from which different consumers can be controlled.
The previously known solutions have the disadvantage that the control block represents a hydraulic resistance for the oil volume stream. For this reason the control block brings about a reduction in the power to be transferred. A reduction of this power loss can be achieved by means of using a larger block having a larger cross-section, but this larger block requires a lot of construction space and is furthermore very expensive.
The lost power of the control block is caused by the flow valves used in the control block. Flow valves correspond to throttle valves in terms of their construction, and allow control of the hydraulic volume stream by way of a changeable pressure loss. The valves of the control block are controlled directly by the operator, by way of a manual controller, for example by means of a joystick (hydraulic pre-controller), or also by way of auxiliary valves, also called pre-control valves, which in turn are activated electrically by the operator. If only one consumer is being operated, for example a vibration pile-driver during pile-driving operation, when a vibrator uses the full power as the sole consumer, the control block does not have any function; it merely serves to pass the oil volume stream through, but does hinder the passage of the oil volume stream as a consequence of the design-related flow resistance.